Analyses of the arenaviruses Pichinde (PIC), Pichinde Munchique (MUC) and the lymphocytic choriomeningitis virus (LCM) strains WE and Armstrong (ARM) have established that arenaviruses have the potential for forming recombinant viruses by viral RNA segment reassortment. Two recombinant virus L/S RNA genotypes (PIC/MUC and WE/ARM) have been obtained and their RNA species characterized by oligonucleotide fingerprint analyses. Tryptic peptide analyses of the PIC/MUC recombinant have established that its virion N polypeptide is coded by the viral S RNA. Analyses of the PIC/MUC recombinant virus plaque phenotype have shown that it has PIC plaque type, likewise analyses of the WE/ARM recombinant have shown that it has a WE plaque type.